<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>后盾人</title>
    <style>
        /* 100 */
        #houdunwang {
            color: blue;
        }

        /* 21 */
        body .hdcms[class] {
            color: red;
        }

        /* 20 */
        .houdunren[class] {
            color: green !important;
        }
    </style>
</head>

<body>
    <!-- 
        0100
        0010
     -->
    <div class="houdunren hdcms" id="houdunwang" style="color:black;">hdcms</div>
</body>

</html>